1. Field of the Invention
The present invention generally relates to a method of operating and controlling a mobile base station in mobile communications systems, and particularly relates to a method of operating and controlling a mobile base station by controlling the operation of a mobile base station connected to a mobile communications system via a wireless relay channel by taking into account radio interference with another base station that is fixedly installed.
Further, the present invention relates to a mobile base station to which such a method of operating and controlling a mobile base station is applied.
2. Description of the Related Art
When a base station is to be newly installed in the mobile communications system, simulation or analysis is conducted regarding radio interference between the newly installed base station and existing base stations in the surrounding area. Based on the findings, operation conditions are determined, including radio communication characteristics such as a frequency to be used, codes to be used, a transmission power, a directionality of radio transmission, and so on, in order to use the new base station in the mobile communications system. The newly installed base station is then operated according to the operation conditions inclusive of the radio communication characteristics that were determined for the mobile communications system.
There are cases in which a mobile base station linked to the mobile communications system via the wireless relay function is to be temporarily installed in an area where a temporal surge of traffic is expected. In such a case, it is not desirable to conduct simulation or analysis regarding radio interference with existing base stations for the purpose of determining the operation conditions each time such a temporary base station is to be installed. If such simulation or analysis must be conducted prior to every such installment, the installment of mobile base stations cannot be conducted with sufficient flexibility and promptness.
A base station that is installed in a vehicle such as a land vehicle, a ship, and an aircraft (such a base station is also referred to as a mobile base station) may be located outside the communication area covered by the fixed base stations of the mobile communications system. For example, a mobile base station installed in a ship on the sea may be operated without taking into account radio interference with the base stations that are fixedly installed on the land. If the vehicle enters the communication area covered by the fixed base stations, such as when the ship makes a stop at a bay, it may be possible to have radio interference between the mobile base station of the vehicle and the fixed base stations.
In order to avoid such radio interference, operation conditions of the mobile base station may be determined in advance by the method as previously described. Even when the mobile base station is operated based on the operation conditions determined in such a manner, however, the movement of the mobile base station to a new point different from the expected point may still create radio interference between the mobile base station and the fixed base stations.
Further, after the operation conditions of the mobile base station are determined with respect to a given point, the operative conditions of the fixed base stations may change in the mobile communications system, or the arrangement of the fixed base stations may change. In such a base, the mobile base station operated according to the predetermined operation conditions may create interference with the fixed base stations.
Accordingly, there is a need for a method of controlling the operation of a mobile base station that makes it possible to properly control the operation of the mobile base station regardless of the position thereof in the mobile communication system.
Further, there is a need for a mobile base station to which such a method of controlling the operation of a mobile base station is applied.